1. Field of the Disclosure
The present disclosure relates to a reducing agent supply device,
2. Description of Related Art
An internal combustion engine mounted in a vehicle in which a selective reduction-type NOx purification catalyst is disposed is known. In this internal combustion engine, a reducing agent supply device is disposed to supply a reducing agent to a part of the exhaust passage on the upstream side of the NOx purification catalyst so that exhaust gas is purified of NOx by reduction by the NOx purification catalyst.
The reducing agent supply device that is disclosed in Japanese Patent Application Publication No. 2014-15856 (JP 2014-15856 A) is provided with an adding valve that injects the reducing agent into a part in the exhaust passage on the upstream side of the NOx purification catalyst, a tank that is connected to the adding valve via a supply path, and a pump for supplying the reducing agent in the tank into the adding valve or suctioning the reducing agent in the adding valve and the supply path back into the tank.
This reducing agent supply device executes a purge control for suctioning the reducing agent in the adding valve and the supply path back into the tank by operating the pump in a state where the adding valve is open based on a stop command for the internal combustion engine. When this purge control is executed, the reducing agent can be inhibited from remaining in the adding valve and the supply path after the internal combustion engine is stopped and the reducing agent can be inhibited from freezing in the adding valve and the supply path until the internal combustion engine is started next time after the internal combustion engine is stopped.
JP 2014-15856 A also discloses the execution of the purge control continuing until the return suction amount of the reducing agent reaches a predetermined reference value and a value that is equal to or higher than a capacity of the supply path being adopted as the reference value. The value that is equal to or higher than the internal capacity of the supply path is adopted as the reference valise as described above so that the remaining of the reducing agent in the adding valve and the supply path after a purge control termination is further reliably prevented.